A new blood-thinning drug could end the use of rat poison as the primary medical treatment to prevent stroke, it was claimed today. For half a century, thousands of patients at risk of stroke have been given warfarin to prevent blood clotting.

But treatment with the drug, commonly used to kill vermin, is risky. Doses have to be carefully watched and adjusted to prevent excessive bleeding from cuts or stomach ulcers, requiring frequent clinic visits. Warfarin can interact badly with other drugs and certain foods, including green vegetables and grapefruit.

The new drug, Pradaxa, works differently and is safer. Patients taking the pill do not have to be constantly checked for signs of overdosing, and can eat what they like. The drug is also much easier to use alongside other medicines. Results from a major trial showed Pradaxa was 34% better at reducing the risk of stroke and blood clots in at-risk patients than well-controlled warfarin.

Death rates were also reduced by 15% when patients were given the drug.

More than 18,000 patients from 44 countries took part in the three-year RE-LY (randomised evaluation of long-term anticoagulant therapy) trial, the largest of its kind ever conducted. Participants had an average age of 71 and all suffered from atrial fibrillation, a heart rhythm disorder that greatly increases the risk of stroke. They were randomly assigned to treatment either with Pradaxa or warfarin.

The findings were presented at the European Society of Cardiology's annual meeting in Barcelona, Spain, and published online in the New England Journal of Medicine.

Professor Stuart Connolly, one of the leading investigators from McMaster University in Hamilton, Canada, said: "The results … exceeded all our expectations. We now have an oral treatment which offers superior protection from stroke with less bleeding and without the need for routine monitoring."At present the drug is only licensed in the UK for the treatment of orthopaedic patients at risk of clotting after surgery. An application for permission to use it for the prevention of stroke is pending.

One leading expert said Pradaxa, which costs around £2.10 a pill, could make warfarin largely redundant.

Dr Adrian Brady, consultant cardiologist at Glasgow Royal Infirmary, said: "This is the greatest step forward in anticoagulation therapy for over 50 years.

"The results presented today could mean the end of warfarin, known by many as rat poison, for many patients – no more anticoagulation clinics, no more blood tests, no more watching what you need to eat and drink. Patients and their doctors will be eagerly examining these findings with a view to switching from warfarin to this new drug once it is licensed."

Atrial fibrillation (AF) affects more than half a million people in the UK and is a leading cause of stroke. Around 150,000 people in the UK suffer a stroke each year.

Worldwide, it is estimated that 3,000 strokes per day could be prevented if AF patients were given Pradaxa instead of warfarin.